Android Mainlining Project

Revision as of 13:57, 2 May 2012 by Tim Bird (talk | contribs) (Patch/Feature Status Chart)
Jump to: navigation, search

This page is for organizing the Android Mainlining Project. It has information and resources associated with this project.


The goal of this project is to ultimately mainline all patches required to run the current released version of Android. The purpose of mainlining these patches is 3-fold:

  1. to allow a developer to use the latest released version of the Linux kernel to run an Android system, without requiring patches to their kernel
  2. to make it possible to develop drivers and board support features against either an Android kernel release or a kernel release, with little or no modifications or conditional code
  3. to reduce or eliminate the burden of maintaining independent patches from release to release for Android kernel developers

To "mainline" a patch means to have it included in Linus Torvalds kernel, in a released (non-rc) version.


[This is a draft section, up for discussion]


  • identify all patches/features, and categorize into core or non/core
    • core = feature is required or strongly desired for Android operation on a platform
    • non-core = Most of the Android system can run without the feature

Per feature or patch:

  • research any previous submission feedback
  • incorporate feedback, as appropriate
  • negotiate any interface changes with Google Android team
  • submit updated patches to mainline
  • repeat until accepted




People who have expressed interest in this project are:

  • Tim Bird
  • John Stultz
  • Paul McKenney
  • Deepak Saxena
  • Arnd Bergmann
  • Thomas Gleixner
  • Arjan Van de Ven
  • Brian Swetland
  • Tetsuyuki Kobayashi
  • Andy Green
  • Victor M. Jaquez
  • Jesse Barker
  • Anton Vorontsov
  • Greg Kroah-Hartman
  • Shuah Khan


This section has miscellaneous notes on roles, capabilities and expertise of group's members

John Stultz is the owner of the Linaro blueprint for mainlining Android features. Tim Bird is the owner of the CE Workgroup project for mainlining Android features. Deepak and Jesse can help make arrangements for a meeting at Linaro Connect. Tim can help make arrangements for a meeting at Android Builders Summit.

  • John Stultz has worked on POSIX Alarm timers
  • Jesse is working on shared memory buffers related to pmem/CMA/parts of ion
  • Anton Vorontsov is looking at the lowmemory killer
  • Greg has put some Android patches into mainline (under drivers/staging/android) previously
    • Greg put some Android patches in mainline under drivers/staging/android in Dec. 2011
  • Paul McKenney - kicking around ideas for dealing with wakelocks single global lock (dec. 2011)


  • Update this site with information on latest patch status - ongoing, by anyone
    • [FIXTHIS - add sections needing a status or status update]

Patch/Feature Status Chart

Feature/Patch Description Status Part of core? Owner/Interested parties Notes
logger kernel support for Android system logging in drivers/staging/android, in kernel version 3.3 2012.03.19 yes Tim Bird See Mainline Android logger project for a list of ideas, issues and a project plan for this feature

Also see this LKML discussion thread Some cleanup patches in linux-next, with more extensive changes to be written, tested, reviewed by Tim in Spring 2012. Tim has some changes to avoid hardcoding the logging channels, but needs to test them before submission to mainline (5/2/2012).

wakelocks Power management locking mechanism to prevent opportunistic suspend not mainlined, as of 2012.03.19, work in progress yes Rafael Wysocki Is important due to impact on board support and drivers by 3rd parties. Last effort was around "autosleep and wakelocks".

See and this thread:

Android alarm timers Timers that count down during suspended operation, and can wake from suspend Partial: Posix alarm timers were mainlined in kernel version 2.6.38 - see yes John Stultz Mending patches to convert Android Alarm Timers to utilize the upstreamed alarm timer work are still pending.
ashmem Shared memory implementation that allows unpinned pages to be marked, which can be dropped by the kernel under memory pressure in drivers/staging/android, in kernel version 3.3 2012.03.19 yes John Stultz Working on fadvise volatile alternative implementation that handles part of the ashmem functionality. However, there are additional aspects of ashmem design that need to be addressed(no tmpfs mounts, atomic create/unlink behavior,etc).
network security special permission checks for secure access to network operations not mainlined ? (can run without it, but network security won't be enforced) no one May be very difficult to mainline, as the code is extremely Android-specific with hardcoded GIDs and capabilities.
binder Android inter-process communication mechanism in drivers/staging/android, in kernel version 3.3 2012.03.19 yes no one Generated a fair amount of discussion on last submission. See

See also this thread:

Android pmem driver manages large (1-16+MB) contiguous physical memory regions to be shared between userspace and kernel drivers (dsp, gpu etc.) Removed - no longer in use yes Shuah Khan Investigating existing alternatives. Can CMA (Contiguous Memory Allocator) fill the need? Based on recent lkml discussion, pmem.c is no longer used and will be removed from Android release. Reference: - Patch to remove pmem.c from 3.3-rc1 staging area has been accepted.
Android USB gadget driver Support for Android as gadget device from host unknown ? (not sure if needed for basic bringup or not, but would be really painful if missing) no one?
timed gpio perform gpio operations as a result of specified timeouts - mainly used to support vibrate feature. in drivers/staging/android, in kernel version 3.3 2012.03.19 no? (is this needed for basic bringup?) Shuah Khan A new transient trigger added to led triggers in Linux 3.4 to address the need for one shot timer activation. This driver could be removed once the legacy libraries are changed to use the new transient trigger.
timed output seems to just be a class for timed gpio items in drivers/staging/android, in kernel version 3.3 2012.03.19 no? (required by timed_gpio) Shuah Khan A new transient trigger added to led triggers in Linux 3.4 to address the need for one shot timer activation. This driver could be removed once the legacy libraries are changed to use the new transient trigger.
low memory killer feature to manage application lifecycle in low memory conditions in drivers/staging/android, in kernel version 3.3 2012.03.19 yes (but system might work without it) Anton Vorontsov See for discussion about these patches
ram console ability to save console output to a reserved ram area for diagnostics on a subsequent boot in drivers/staging/android, in kernel version 3.3 2012.03.19 no Shuah Khan No lkml submission attempt history found so far. pstore fs interface solves the same problem and is in mainline 3.1.5. fs/pstore Reference - After investigating and discussing ram console use cases, it is clear that the proposal to use ram-oops and pstore will not be a complete solution to cover all the cases. Hence, the going forward plan is to pursue ram console inclusion in the mainline. ram console is going through re-write splitting it into twp drivers. Waiting for these changes to get into the 3.3 staging area. For now working with the unofficial patches.
ion graphics memory driver graphics memory drivers thingie not mainlined yes (for 4.0 and later?) Jesse Barker

Progress Chart

This section is intended to show our progress, by showing the patch set size over time. With any luck, as we get features into mainline, the difference between the Android kernel and the mainline Linux kernel will shrink.

Note: This table is not up-to-date and is hard to measure anyway. The inclusion of a lot of material into 3.3 obsoletes the need for a per-patch tracking mechanism (maybe?). Also, there will always be some difference, due to board support packages and new development areas (like ion), so the goal is not really 0 differences, but just a reduction overall. I'm not sure if we'll maintain this table or not, but I'm leaving it for now as a placeholder.

  • diff of 2.6.29 tree versus kernel
Kernel Version Files changed insertions deletions hunks bytes in diff
2.6.29 187 123506 0 187 3291827